[816] Patients with Recurrent Prostate Adenocarcinoma Show Higher Levels of Somatostatin Receptor 2 Expression

NE Lueck, CM Simons, RD Williams, TM O'Dorisio, MS O'Dorisio, BR DeYoung. University of Iowa Hospitals and Clinics, Iowa City, IA

Background: Numerous studies have explored the role neuroendocrine differentiation plays in prostate adenocarcinoma (PA) prognosis, with mixed results as to its clinical significance. Because at least some studies have suggested a worse prognosis in PA with neuroendocrine differentiation, there has been an interest in determining somatostatin receptor expression in those tumors showing neuroendocrine differentiation stemming from the possibility of employing somatostatin analogues as treatment. To date, however, no study has examined the relationship between neuroendocrine differentiation, somatostatin expression and outcome in PA.
Design: 26 patients with recurrent prostatic adenocarcinoma and 25 patients who, after 10 years of follow-up, were free of recurrent prostatic adenocarcinoma were matched according to Gleason score and margin status at prostatectomy. Immunohistochemical staining utilizing standard technique with formalin fixed paraffin embedded tissue from each patient's prostatectomy specimen was performed with primary antibodies to chromogranin (DAKO, 1:200 dilution), synaptophysin (DAKO, 1:50 dilution) and a novel antibody to somatostatin receptor 2 which has been previously characterized in the literature. Percent of tumor cells with staining for chromogranin, synaptophysin and somatostatin receptor 2 was recorded.
Results: Neuroendocrine differentiation as defined by either chromogranin or synaptophysin staining of 5% tumor cells was seen in 7 patients with recurrent PA and 4 without recurrence. In patients with recurrent PA, a higher percentage of tumor cells expressing somatostatin receptor 2 was observed when compared to the tumors from patients without recurrence (p = 0.058).
Conclusions: Patients who exhibited recurrence of their prostatic adenocarcinoma showed increased levels of somatostatin receptor 2 expression. While the underlying pathobiology requires further investigation, the findings may provide some rationale for the use of somatostatin analogue treatment for patients with recurrent or advanced prostate adenocarcinoma.
Category: Genitourinary (including renal tumors)

Monday, March 9, 2009 9:30 AM

Poster Session I Stowell-Orbison/Autopsy Award # 128, Monday Morning